The invention relates to improvements in hydraulic operating arrangements, particularly to operating arrangements for clutches in the power trains of motor vehicles. More particularly, the present invention relates to improvements in hydraulic operating arrangements which can be utilized with advantage in or in combination with so-called master and slave cylinders to actuate friction clutches between the prime movers (such as internal combustion engines) and the change-speed transmissions in the power trains of motor vehicles.
Published German patent application No. 197 42 468 discloses a clutch operating arrangement wherein the housing or casing of the slave cylinder consists, at least in part, of a plastic material. Such slave cylinders are known as central clutch release devices and their casings are normally affixed to the transmission housing or case by threaded fasteners. At least a part of the casing of the slave cylinder is mounted in such a way that it surrounds the input shaft of the change-speed transmission. Securing of the casing of the slave cylinder to the transmission case by threaded fasteners during assembly of the power train is time consuming and hence expensive.
Presently known seals, such as lip seals, which serve to seal the internal chamber of the casing of the slave cylinder from the atmosphere when such chamber is to receive hydraulic fluid from the master cylinder are normally mounted on the reciprocable piston in the slave cylinder of a brake actuator. Such seals share the axial movements of the piston and are called upon to move along inner and outer sealing surfaces which are respectively provided on a metallic and on a plastic material. The sealing surface which is provided on a plastic material normally offers a greater frictional resistance to axial movements of the piston and is likely to generate noise while guiding a piston during actuation (such as disengagement) of the friction clutch.
It is also known to provide the slave cylinder in the hydraulic clutch actuating system of the power train in a motor vehicle with an internal sleeve which serves to guide the piston of the slave cylinder and is made of steel or an equivalent material. A drawback of such slave cylinders is that adequate sealing of the contact surface(s) between the guide sleeve of steel and the plastic casing of the slave cylinder can create serious problems. In order to avoid such problems (including high cost or an unsatisfactory seal), the casings or cylinders of many presently known slave cylinders do not employ separately produced guide sleeves for the piston, i.e., the guide sleeve is part of the plastic casing. A drawback of such proposals is that the making of a slave cylinder casing without a separately produced guide sleeve for the piston but with an adequate guide surface for the piston (i.e., with a guide surface provided on a part made of a plastic material) cannot be made at a reasonable cost in available machines, e.g., in standard injection molding machines for the making of articles from plastic material. As a rule, an injection molding machine which is to turn out such plastic slave cylinder casings must be equipped with highly complex parts such as shifting or pushing arrangements and the like.
An object of the present invention is to provide a slave cylinder, especially a slave cylinder which can be used as a friction clutch release unit in the power train of a motor vehicle, which does not exhibit the aforediscussed drawbacks of conventional slave cylinders and which exhibits numerous important advantages over such conventional parts or groups of parts.
Another object of our invention is to provide a slave cylinder which can be turned out in large numbers in conventional injection molding and other available machines.
A further object of the invention is to provide a slave cylinder which can be integrated into existing types of power trains without any or without appreciable modifications of such power trains.
An additional object of the invention is to provide a slave cylinder which can be installed within the clutch bell under the hood of a motor vehicle.
An additional object of the invention is to provide a slave cylinder which requires a minimum of maintenance, no inspection or infrequent inspection, and whose useful life is longer than that of presently known slave cylinders for use as a means for actuating friction clutches in the power trains of motor vehicles.
Still another object of the instant invention is to provide a hydraulic clutch actuating system the condition and mode of operation of which can be expected to remain unchanged during the useful life of the motor vehicle.
A further object of the invention is to provide a slave cylinder which can be readily sealed where necessary, wherein the casing is in optimal frictional engagement with the piston, which is not subject to excessive wear, the material of which is not likely to exhibit pronounced fatigue after relatively short periods of use, and which can be made of a wide variety of readily available materials.
Another object of the invention is to provide a hydraulic operating arrangement which employs the above outlined slave cylinder.
A further object of the present invention is to provide novel and improved adapter means for use in the connection between a master cylinder and a slave cylinder in the power train of a motor vehicle.
An additional object of the invention is to provide novel and improved methods of making various component parts of the means for actuating the friction clutch in the power train of a motor vehicle.
Still another object of the invention is to provide novel and improved materials and/or combinations of materials for the making of casings which are to form part of slave cylinders in the power trains of motor vehicles.
A further object of the invention is to provide novel and improved means for ventilating the chambers of cylinders or casings forming part of slave cylinders.
One feature of the present invention resides in the provision of a system for altering the bias of a clutch spring (such as a diaphragm spring) in and for thus changing the condition of an engageable and disengageable friction clutch between a rotary output element (such as a crankshaft or a camshaft) of a prime mover (such as an internal combustion engine) and a rotary input element of a change-speed transmission preferably having a composite housing or case and being disposed in the power train of a motor vehicle. The improved system includes a primary unit (such as a master cylinder) having an output, means (such as a clutch pedal or an electronic actuator) for actuating the primary unit to thus transmit a pulse by way of the output of the primary unit, a clutch release device having an at least partially plastic composite casing and a mobile bearing coaxial with the input element of the transmission and arranged to alter the bias of the clutch spring in response to movement axially of the input element, means for operatively connecting the output of the primary unit with the clutch release device to move the bearing axially of the input element in response to actuation of the primary unit to transmit a pulse by way of the output, and means for coupling the clutch release device to a component of the transmission housing which is preferably located opposite the bearing.
The means for actuating the primary unit (such as the aforementioned master cylinder) can comprise a driver-operated pedal (clutch pedal) in the motor vehicle.
The coupling means which connects the clutch release device with a component of the transmission housing can include a self-locking arrangement.
The aforementioned master cylinder can constitute a first hydraulic cylinder and piston unit of the improved system, and the aforementioned output can constitute an outlet of the cylinder of the first unit. The casing of the clutch release device can include or constitute the cylinder of a second hydraulic cylinder and piston unit having a mobile piston which is operatively connected with the bearing and is reciprocable in the casing. The actuating means of the improved system can include a conduit which connects the outlet of the cylinder of the first unit with the cylinder of the second unit.
The coupling means of the improved system can comprise complementary first and second coupling members which are form-lockingly connected to each other and are respectively provided on the housing and on the casing. The second coupling member can be of one piece with the casing, and such casing can constitute an injection molded part. The second coupling member can have a shape which is imparted thereto exclusively by injection molding.
It is also possible to employ coupling means which includes at least one snap fastener. The housing of such system is preferably coaxial with the casing and the snap fastener can include at least one hook provided on the housing or on the casing and at least one opening receiving the at least one hook and provided either in the casing or in the housing against axial movement relative to the housing. Alternatively, the at least one snap fastener can comprise an annular array of male fastening elements provided on one of the casing and housing and at least one female fastener provided in the other of the casing and housing and receiving the male fastening elements. The at least one female fastener can include an annular array of openings, at least one for each of the male fastening elements.
The casing of the clutch release device can include a cylinder and this device can further comprise an annular piston which is provided in the cylinder and is arranged to move the bearing relative to the input element (such as a shaft) of the change-speed transmission. The bearing and the piston of such clutch release device surround the input element of the transmission.
Another feature of the present invention resides in the provision of a device which is set up to operate a clutch (such as a friction clutch) between a prime mover and a change-speed transmission in the power train of a motor vehicle. The improved device comprises an axial extension which is provided on the case or housing of the transmission and has a radially inwardly extending circumferetially segmented (subdivided or partitioned) profile, and a casing having an enlarged portion projecting radially outwardly of and overlying (i.e., being surrounded by) at least a portion of and engaging the extension by snap action or an analogous or equivalent action to thus secure the casing to the transmission case as seen axially as well as radially of the extension.
A further feature of our invention resides in the provision of a device for operating a clutch between a prime mover and a change-speed transmission in the power train of a motor vehicle. The device includes an axial extension provided on the transmission case and having a radially extending profile which is provided with a circumferentially extending groove, and a casing having an enlarged portion overlapping or being overlapped by a portion of the extension and engaging the latter by snap action. The engaging means includes at least one fastener which extends into the aforementioned groove of the axial extension of the transmission case.
An additional feature of the instant invention resides in the provision of a device for operating a clutch between the prime mover and the change-speed transmission in the power train of an automobile or another type of motor vehicle. The device comprises an axially enlarged tubular extension provided on the transmission case and having a segmented external profile, and a casing having at least one snap fastener which projects radially inwardly of the extension and engages the external profile to thus secure the casing to the transmission case.
The external profile of the tubular extension can define an annular recess, and the at least one snap fastener extends into the annular recess of the external profile.
The casing of the device includes a portion which is received in the tubular extension, and the aforementioned portion of the casing can further serve as a means for centering the casing relative to the extension.
Another feature of our invention resides in the provision of a device for operating a clutch between a prime mover and a change-speed transmission in the power train of a motor vehicle. The improved clutch operating device comprises a casing including a portion confronting a part of the transmission case, and at least two substantially pin-shaped projections which are provided on the casing and are received in complementary recesses provided therefor in the aforementioned part of the transmission case. The projections have deformable portions extending into the respective recesses and frictonaly engaging the aforementioned part of the transmission case.
The deformable portions extend radially beyond the respective projections and the openings can be dimensioned in such a way that they receive the respective projections with lateral play but effect deformation of deformable portions in response to insertion of the projections into the respective openings so that the deformable portions are self-lockingly retained in the respective openings. The dimensions of the deformable portions (each such deformable portion can include one or more elastic laminations) can decrease in directions as seen into the respective openings.
An advantage of the just described embodiment is that the pin-shaped projections can cooperate with the aforementoned part of the transmission case to hold the casing and the case against axial and angular movement relative to each other. Furthermore, the openings (such as blind holes) can be provided in the casing and the projections are then provided on the transmission case. It is also possible to provide one or more projections on the casing and to further provide one or more projections on the transmission case. The deformable portions can constitute washer-like resilient components which surround the respective pin-shaped projections.
All of the projections may but need not be identical and the radially outer portion of each washer-like deformable portion can be provided with cutouts to facilitate flexing of such deformable portions during insertion into the respective openings.
The just described mode of non-rotatably coupling two parts to each other with simultaneous holding of the parts against axial movement relative to each other can be utilized with advantage in numerous devices or arrangements other than those which serve to releasably couple parts in a clutch actuating device for use in the power trains of motor vehicles.
An additional feature of our invention resides in the provision of a hydraulically actuatable slave cylinder unit for operating a clutch between a prime mover and a change-speed transmission in the power train of a motor vehicle. The improved slave cylinder unit comprises a plastic casing, a guide sleeve which is provided in the casing and surrounds the input shaft of the transmission, an annular piston which is reciprocable in an annular chamber of the casing and surrounds the sleeve, a clutch-operating release bearing which is provided in the chamber and is affixed to the piston, and means for securing the sleeve to the transmission case or to the casing. The means for securing includes a radially outwardly extending flange which is provided at one end of the sleeve and is adjacent the transmission case. The flange has a radially outer portion which is received in a groove of the casing, and the securing means further includes at least one retaining member which is provided in the casing and cooperates with the radially outer portion of the flange to hold the casing and the sleeve against axial movement relative to each other.
The radially outer portion of the flange can include an annular array of extensions which form part of a bayonet mount of the at least one retaining member.
Furthermore, the at least one retaining member can form an integral part of the casing and can be deformed to overlie the radially outer portion of the flange subsequent to insertion of the radially outer portion into the groove.
The at least one retaining member can be deformed as a result of a treatment preferably involving hot caulking or ultrasonic caulking.
The guide sleeve can be received in the casing in stressed condition, and this guide sleeve can cooperate with the casing to jointly define the annular chamber. The improved slave cylinder unit can further comprise at least one sealing element which is interposed between the casing and the sleeve. Such at least one sealing element can constitute an O-ring, a flat seal, a liquid seal or a flow seal. The flow seal can consist of or include a solidified flowable substance which is received in an annular groove of the casing; such solidified flowable substance can consist of or contain silicon rubber or silicon resin. This flow seal can be disposed radially outwardly of the chamber and the casing can be provided with at least one inlet for admission of the flowable substance into its groove. The groove for the flowable substance can have a diameter which slightly exceeds the diameter of the chamber.
The flow seal can have a ring-shaped sealing surface and the casing can be provided with an axially raised sealing surface which surrounds the inlet, which is engaged by the flow seal, and which is in sealing engagement with the radially outer portion of the sleeve.
The slave cylinder unit can further comprise a stop for the release bearing or the piston, and such stop is or can be remote from the aforementioned flange. For example, the stop can be of one piece with the sleeve and can be arranged to prevent disengagement of the piston and of the bearing from the sleeve in storage and/or during transport of the casing, e.g., from the manufacturing plant to the automobile assembly plant.
The stop can constitute a deformed portion of the sleeve; for example, such stop can include at least one substantially radially outwardly extending tongue of the sleeve and such tongue can extend at least substantially circumferentially of the sleeve.
The guide sleeve can consist, at least in part, of a plastic material and the stop can be of one piece with such guide sleeve and/or with the casing.
Another feature of the invention resides in the provision of a hydraulically operated disengaging system for a friction clutch in the power train of a motor vehicle wherein the clutch is installed between a prime mover and a change-speed transmission. The improved system comprises a master cylinder unit, a slave cylinder unit which includes a casing and an annular piston which is reciprocable in an annular plenum chamber of the casing, means for conveying pressurized hydraulic fluid from the master cylinder unit into the plenum chamber, and an annular lip seal provided in the chamber and being slidable relative to cylindrical internal and external surfaces which are provided within the casing radially outwardly and inwardly of the chamber. The casing includes at least one cylindrical metallic sleeve and one of the aforementioned surfaces is provided on the at least one sleeve.
The arrangement can be such that the external surface is provided on the sleeve.
The casing can comprise two cylindrical metallic sleeves one of which is provided with the internal surface and the other of which is provided with the external surface.
The at least one sleeve can consist, at least in part, of aluminum, steel, titanium and/or the alloys of such metals.
Furthermore, the at least one sleeve can include a film which is provided with the at least one surface and serves to reduce the coefficient of friction between the at least one sleeve and the lip seal. The film can contain or consist of grease or of a metal ennobling material.
The at least one sleeve can be provided with a substantially radially outwardly projecting extension and the lip seal is then disposed in the chamber between the piston and the extension. The latter has a sealing surface which abuts a plastic portion of the casing, and such disengaging system can further comprise a second seal which is interposed between the plastic portion of the casing and the extension, a cover which overlies the extension opposite the second seal, and means for securing the cover to the plastic portion of the casing. Such securing means can include an at least substantially annular joint which can be a welded joint, an adhesive joint or a detent.
Still another feature of our invention resides in the provision of a hydraulically operated disengaging system for a friction clutch in the power train of a motor vehicle wherein the clutch is installed to operate between a prime mover and a change-speed transmission. The improved system comprises a master cylinder unit and a slave cylinder unit which latter includes a composite casing consisting at least in part of a plastic material. The slave cylinder unit further includes an anular piston which is reciprocable in an annular plenum chamber of the casing and the latter includes at least two sections which are separable or are separately produced parts to facilitate sealing of the chamber from the atmosphere. Such disengaging system further comprises means for conveying pressurized hydraulic fluid from the master cylinder unit into the annular plenum chamber; the conveying means includes at least one extension provided on the casing.
The extension can include a pipe which is provided with at least one channel for delivery of pressurized fluid from the master cylinder unit into the chamber. The casing can be of one piece with the pipe, and such pipe as well as the casing can consist of a plastic material. The disengaging system can further comprise a bell which confines the friction clutch and the slave cylinder unit. The pipe extends from the master cylinder unit through and into the bell.
The extension can include a nipple and a conduit which is coaxial with and communicatively connects the nipple with the plenum chamber.
The casing can include a wall which is adjacent an end of the chamber and has an opening for the flow of fluid from the conduit into the chamber. This casing can constitute an injection molded product and can be provided with at least one aerating port. Such disengaging system can further comprise means for sealing the at least one port; such sealing means can be secured to the casing by welding, threading, the use of adhesive and/or by latching with the interposition of at least one sealing element between the casing and the sealing means.
A further clutch disengaging system which embodies the present invention comprises a master cylinder unit and a slave cylinder unit including a casing and an annular piston which is reciprocable in an annular plenum chamber of the casing. The casing consists, at least in part, of a plastic material, and the system further includes means for conveying pressurized hydraulic fluid from the master cylinder unit into the chamber and at least one sensor which is associated with the casing and serves to monitor the positions of the piston in the chamber. For example, the sensor can be set up to monitor distances which are covered by the piston in the chamber. Such sensor can be at least partially embedded in the casing, and such casing can constitute an injection molded article. The means for conveying can include a tubular extension of the casing, and such system can further comprise conductor means which is or are embedded in the extension and is or are connected with the at least one sensor.
Another embodiment of the improved hydraulically operated clutch disengaging system comprises a master cylinder unit and a slave cylinder unit which includes a casing and an annular piston slidably reciprocable in an annular chamber of the casing. The casing consists at least in part of a plastic material and contains at least one component which serves to reduce sliding friction with the piston, and the system further comprises means for conveying pressurized hydraulic fluid from the master cylinder unit into the plenum chamber.
The sliding friction reducing component can consist of graphite and/or a polyfluorohydrocarbon; such component can constitute between about 5% and 20%, preferably between 8% and 15% of the material of the casing. A satisfactory casing can contain between about 35% and 75% of a plastic material (such as a thermoplastic or thermosetting substance), between about 20% and 45% of fibers (such as glass fibers which strengthen the casing), and between about 5% and 20% of sliding friction reducing material.
A further embodiment of the improved hydraulically operated clutch disengaging system can comprise a master cylinder unit and a slave cylinder unit which latter includes a casing having an annular plenum chamber, an annular piston reciprocable in the chamber, a first cylindrical surface surrounding the chamber, a second cylindrical surface surrounded by the chamber, and an annular lip seal which is disposed in the chamber, which sealingly engages the two surfaces and which is reciprocable with the piston along and in sealing engagement with predetermined portions of the two surfaces. The slave cylinder further comprises a metallic film provided at least on the predetermined portion of at least one of the surfaces, and the clutch disengaging system further comprises means for conveying pressurized hydraulic fluid from the master cylinder into the plenum chamber.
A further embodiment of the improved clutch disengaging system comprises a master cylinder and a slave cylinder including a casing and a metallic sleeve which is received in and defines with the casing and annular chamber. The sleeve has limited freedom of radial movement relative to the chamber and the slave cylinder further comprises an annular piston which is reciprocally received in the chamber and an annular lip seal which is reciprocable in the chamber with the piston and has an internal surface which sealingly engages the sleeve and an external surface which sealingly engages the casing. The disengaging system further comprises means for conveying pressurized hydraulic fluid from the master cylinder into the annular chamber.
A further fluid-operated clutch actuating system of the present invention comprises a master cylinder, and a slave cylinder including a casing defining a chamber and a piston which is reciprocable in the chamber to thus effect actuation of the clutch. The clutch actuating system further comprises means for conveying fluid between the master cylinder and the chamber of the casing in the slave cylinder. The fluid conveying means comprises an aerating device with at least one sealable port for evacuation of fluid from the chamber.
Another fluid-operated clutch actuating system of the present invention comprises a master cylinder unit and a slave cylinder unit including a preferably plastic casing and a piston which is reciprocable in a chamber of the casing to thus actuate the clutch. The actuating system further comprises means for conveying fluid from the master cylinder unit into the chamber to thus move the piston relative to the casing, and such fluid conveying means includes an adapter which is separably connected with the master cylinder unit and/or with the slave cylinder unit.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved clutch actuating system itself, however, both as to its construction and the modes of assembling, installing and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.